This is late information, but may be useful to others who come across this in a search.
I have been testing several AM2302 (aka DHT22). Here in the Houston, Tx area we often have long periods of very high humidity.
Thus far all the DHT22's I have placed outdoors (under a roof so they are not subject to rain or any direct moisture) have begun giving false humidity readings after a day or two. The typical day has been between 70% and 100% humidity with the temperature between 70F (21C) and 94F (34C).
[N.B., yes that is correct, our dewpoint has not been below 21C for the last 4 weeks]
In the failure mode the sensors continue to give humidity readings but the readings are about 15% RH too high.
It appears this is a saturation problem and basically renders them useless for anything except air conditioned spaces.
Caveat Emptor.